Armysets are in here. Each armyset consists of a set of army descriptions, a
name, a size and a unique(!!) id.

Furthermore, each armyset contains an image (40*(#armies) x 40 currently) and
a mask to map player colors. The mask has to be an image with indexed palette;
For the colors to be used, see the comments in player.cpp (function
Player::initPalette).
Mask and image files need to have the same name as the armyset description file
and have to be .png files.

The currently used indexes are:

1 - standard armies (available for all players)
2 - Heroes (_not_ to be assigned to any player); they are handled specially
3 - Imperial troops
4 - Monsters
5 - Orcs

All indexes above 5 are free as of now.

Note that the indexes 1 and two should always stay the same; we identify the
standard armyset by index 1 and the heroes by index 2.
